The best choice for the question: Short-term climate change can be explained by the Milankovitch theory and its cycles, would be: C: False: the orbital changes occur on 21.000 to 23.000 year cycles.
The Milankovitch Cycles and Glatiation, is a theory that was created by Serbian Milutin Milankovitch, an astronomer and mathematician who dedicated himself to study the long-term changes in the periods of glatiation and lack of it, on Earth. He discovered that these changes in climate, especially the appearance of Ice Ages, or not, depended more on the position of the Earth with respect to the Sun, Earth´s gravitational movements around the Sun, the way the Sun´s rays hit the Earth depending on the type of movement it is performing, and whether the Earth is tilted one way or the other on its two axes when it revolves around the Sun. These ideas, which were called cycles, explained the appearance of seasons, and also the big climatic changed on Earth. According to the theory itself, changes in Earth´s orbital movements happen around every 23.000 years, and for its elipses to change around the Sun, around 100.000 years. Also, Earth´s change in the axial tilt, which hapens every 41.000 years, explains the changes in seasonal severity.